The present invention relates to a tubular belt conveyor having an endless belt which is held in a flattened form at the upstream supplying end and downstream discharging end of the conveyor but is rounded along its neutral axis at its intermediate portion such as to wrap and conceal the material which is being conveyed by the conveyor.
Tubular belt conveyors of the type mentioned above are widely used in the transportation of ores because they can effectively prevent flying and scattering of ore, powders and dust while avoiding the risk of ores dropping off the conveyor. A typical example of the tubular belt conveyor of the kind described employs a flat endless conveyor belt which is rounded along the breadth thereof such as to form a "tube" with both longitudinal sides thereof abutting each other in such a manner as to form a radially extending lug along the length of the belt. More specifically, in this known tubular belt conveyor, a pair of beads are formed on the reverse side of the belt in the flattened state along both longitudinal side edges such that, when the belt is bent and the longitudinal side edges of one surface are brought together to form the "tube", the pair of beads in combination form a longitudinal lug, leaving recesses between the lug and the tube portion of the belt on both sides of the lug in such a manner as to form a neck. In the operation of this tubular belt conveyor, a pair of carrier rollers engage with this neck such as to pinch and suspend the running belt.
In this known tubular belt conveyor, however, the following problems are encountered due to the presence of longitudinal beads on the reverse side of the belt along both longitudinal side edges.
(1) At the material feeding and discharging ends of the conveyor, the belt is guided or driven by pulleys. In order to attain a close fit of the belt to the pulleys, the breadth of the pulleys has to be smaller than the overall breadth of the belt. Consequently, the portions of the belt contacted by both longitudinal edges of the pulleys are worn locally and more heavily than other portions of the belt.
(2) The beads are liable to be cut, particularly when the belt runs along a winding path.
(3) The production of a belt having a complicated cross-section around the beads requires a special mold for vulcanization.
(4) The winding or coiling of the belt for packaging purposes is difficult and the size of the package becomes large due to the presence of the beads.